1. Field of the Invention
The present invention relates generally to energy absorbers and energy absorption systems, and more particularly, to a rotary magnetorheological damper for shock and vibration energy absorption systems.
2. Description of Prior Art
The primary function of a shock and vibration protection system is to minimize the potential for equipment damage and/or personnel injury during shock and vibration loading. Such systems are important for vehicular applications, including aircraft, ground vehicles, marine vehicles, etc. Severe shock events may include harsh vertical or crash landings of aircraft, under body explosions of military ground vehicles, horizontal collisions of automobiles, and severe wave-to-hull impact of high speed watercraft. Lower amplitude shock and vibration tend to result from normal operation of such vehicles, including aircraft air loads or rotor loads, ground vehicles traversing rough terrain, etc. The severity of equipment damage and/or personnel injuries can be considerably minimized if the vehicles are equipped with shock and vibration protection systems.
Most current shock and vibration protection systems are passive, in that they cannot automatically adapt their energy absorption as a function of payload weight or as a function of real-time environmental measurements such as shock level, impact velocity, vibration levels, etc. Moreover, some energy absorbers are essentially rigid and do not stroke until the load reaches a tuned threshold. Because of this, these systems provide no isolation of vibration. This motivates the development of a shock and vibration protection system that utilizes an electronically adjustable adaptive energy absorber that can provide adaptive energy absorption for enhanced crashworthiness as well as vibration mitigation.
Magnetorheological (MR) technology is particularly attractive for shock and vibration protection systems as an MR fluid based device can offer an innovative way to achieve what is effectively a continuously adjustable energy absorber, in combination with a real-time feedback controller, can automatically adapt to payload weight and respond to changing excitation levels. With its ability to smoothly adjust its load-stroke profile, MR energy absorbers can provide the optimum combination of short stroking distance and minimum loading while automatically adjusting for the payload weight and load level. Furthermore, MR energy absorbers offer the unique ability to use the same system for vibration isolation.
One key challenge in vehicular applications involving MR energy absorbers is the device weight and size associated with providing sufficient stroke and force capability. Often, a large and massive energy absorbing device is not a possibility due to design and structural constraints. MR energy absorbers having large controllable range, stroke, and bandwidth are needed to provide adaptation to payload weight, shock energy, speed, and required energy absorption. Many MR energy absorbers for shock and vibration isolation mounts have been disclosed such that the damping level can be controlled in feedback by applying a magnetic field (U.S. Pat. No. 5,277,281 to J. D. Carlson et al., U.S. Pat. No. 6,279,700 to H. Lisenkser et al., U.S. Pat. No. 6,311,810 to P. N. Hopkins et al., U.S. Pat. No. 6,694,856 to P. C. Chen and N. M. Wereley, U.S. Pat. No. 6,953,108 to E. N. Ederfass and B. Banks, U.S. Pat. No. 6,481,546 to M. L. Oliver and W. C. Kruckemeyer, and U.S. Pat. No. 6,983,832 to C. S. Namuduri et al). See also, U.S. Pat. No. 6,694,856 issued Feb. 24, 2004 to Chen et al. which includes test data obtained from a COTS Lord Rheonetics® MR damper including force vs. piston behavior. The size and weight of these conventional linear-piston MR damper designs for such applications can make their use prohibitive. Hence, the development of more compact MR devices with the capability to adapt to shock and vibration conditions is of great interest.